Blood Coagulation: Factor X (Stuart factor) is a plasma protein which is required for blood coagulation. It plays a central role in the coagulation process since it can be activated independently by either the intrinsic or extrinsic coagulation system. Factor X can also be activated by several nonphysiological mechanisms and these include its activation by trypsin and a protein from Russell's viper venom. Recent results in our laboratory have shown that the activation of factor X by a protein purified from Russell's viper venom results in the splitting of a glycopolypeptide from the amino terminal end of the heavy chain of the precursor protein. This reduces the molecular weight of factor X from 55,000 to 44,000 and leads to the formation of a new amino terminal isoleucine residue in factor Xa. The work proposed for the next year will extend these studies to test whether factor X activation by (1) tissue factor and factor VII or (2) by factor VIII and factor IXa proceeds by a similar mechanism. RNA Metabolism: When E. Coli enters stationary phase by carbon source or amino acid depletion, etc., r-RNA synthesis decreases 10-20 fold and m-RNA synthesis decrease 2-4 fold. A potent inhibitor of RNA polymerase has been isolated and partially purfied from stationary phase MRE 600 E. Coli and this inhibitor is absent in mid-log bacteria. The nature of this inhibitor and its mode of action will be investigated in detail during the next year.